A circular disk has surface charge density 30 nCcm2 What wil

A circular disk has surface charge density 30 nC/cm^2. What will the surface charge density be if the radius of the disk is doubled? Express your answer to two significant figures and include the appropriate units.

Solution

Q = surface charge density * area

Q is constant

=> S1*A1 = S2*4A1

=> S2 = 30/4 = 7.75 nC/cm^2